SUMMARY OF THE PRESENT INVENTION
The present invention relates to a process for resurfacing roads that have deteriorated due to traffic usage and/or environmental factors. The present invention is particularly applicable to primary and secondary roads formed of asphalt. Resurfacing of such roads can eliminate, or alleviate, various types of road deterioration, e.g. cracks, small pits, erosion of asphalt, and dislocation of aggregates from the road surface.
One current prior art practice used in resurfacing secondary asphalt roads, involves spreading a mixture of asphalt and a volatile solvent onto the degraded road surface, and then depositing a layer of aggregates onto the asphalt-solvent mixture. One volatile.solvent currently used in such resurfacing is kerosene. The solvent is mixed with the asphalt in order to produce a flowable material capable of being distributed at a relatively uniform thickness layer on the road surface, i.e. a tacky layer without ridges or bare spots. Very often the mixture is heated to achieve flowability and a tacky surface.
One difficulty with the above-described process is that the solvent tends to vaporize, which then presents an air pollution problem. The 1990 Federal Clean Air Act and some state air pollution regulations require that vaporization of solvent be no greater than five (5) percent when a sample of the asphalt-solvent mixture is subjected to a distillation test at a temperature: of five hundred (500) degrees Fahrenheit. In many cases asphalt-solvent mixtures used in the past are not able to pass the distillation test.
Another difficulty with the above-described process, using an asphalt-solvent mixture, is that the flowable mixture tends to produce an undesired, runoff, from the road surface. Desired flowability of the mixture for easy spreading on the road surface is not readily controlled within desired limits, so that occasionally the material runs off the road surface onto the adjacent terrain. Such runoff can pose a ground water contamination problem if it is not controlled, or curtailed.
A second, current practice, used in resurfacing of secondary roads, involves spraying an asphalt emulsion onto the deteriorated road surface to form a tacky film; aggregates are then spread onto the tacky film to form a new road surface.
Typically, the asphalt emulsion comprises asphalt, an emulsifying agent, and water; the emulsifying agent can be a surfactant, or soap, capable of causing asphalt to disperse as globules in a continuous water phase.
One problem with road resurfacing processes, using asphalt emulsions, is that the water in the emulsion will not readily evaporate in damp or cool (45 degrees Fahrenheit) conditions making it susceptible to curing related problems.
Other problems associated with the use of emulsified asphalt in road resurfacing, are undesired air pollution (due to emission of volatile organic compounds into the atmosphere) and relatively low cohesion between the asphalt and the aggregates. The aggregates are prone to break away from the road surface due to tire-road surface friction engagements.
The present invention relates to a road resurfacing process wherein asphalt is mixed with waste lubricating oil, sometimes referred to as "specification waste oil", to form a tacky film on a road surface; aggregates are then spread on the tacky film to form a new road surface.
The process of the present invention is advantageous in that air pollution problems are greatly minimized, such that the road resurfacing operation can be performed in the relatively hot summer months, as well as in the colder months. Waste lubrication oil used in the present process has a relatively low volatile organic content, so that air pollution is not a problem, even in the hot summer months of the year.
In the preferred practice of the present invention the asphalt and waste oil are mixed with minor quantities of a finely divided rubber latex and an anti-stripping agent resistant to elevated temperatures. The flowable mixture is heated to a relatively high temperature in the range of 220 to 250 degrees Fahrenheit, such that when the mixture is sprayed onto a deteriorated road surface, the flowable material is sufficiently non-viscous to flow into small cracks and crevices in the road surface.
Aggregates are then spread onto the tacky flowable material while the material is still in a heated condition. The finely divided rubber latex retains the aggregates in place while the asphalt is cooling to the solid state; the latex particles are bonded to each other and to the aggregates aided by the anti-strip in the mixture so as to achieve a continuous non-porous road surface having a relatively good resistance against tire friction forces tending to dislodge aggregates out of the road surface.
The rubber latex particles bond to each other and to the aggregates to provide a containment network for the asphalt and the waste oil. Experience with the process of this invention indicates that the containment network prevents liquid runoff from the road surface. Further, ground water contamination is not a problem with the process of this invention.
The present invention provides a relatively economical process for resurfacing secondary roads without polluting the air or the ground water in the vicinity of the resurfaced road. Also, the invention provides a market for waste oil that is collected in large quantities, on a regular basis at recycling centers and oil-change facilities throughout the country.
In summary, and in accordance with the above discussion, the foregoing objectives are achieved in the following embodiments.
1. A process for resurfacing roads comprising:
(a) mixing asphalt, waste oil, synthetic rubber latex, and adhesive together to provide a flowable mixture comprised of from about sixty (60) percent to about ninety-five (95) percent asphalt, from about forty (40) percent to about five (5) percent waste oil, from about one-half (1/2) percent to about one and one-half (11/2) percent latex and about one-half (1/2) percent anti-stripping agent;
(b) heating said flowable mixture to a temperature of from between about two hundred twenty (220) degrees Fahrenheit to about two hundred fifty (250) degrees Fahrenheit;
(c) spraying said heated flowable mixture onto a road surface to form a tacky heated film on the road surface;
(d) depositing a layer of aggregates onto said tacky heated film; and
(e) running a pressure roller over the aggregate layer to cause the aggregates to be embedded in the tacky heated film.
2. The process, as described in paragraph 1, wherein step (c) is carried out so that the tacky heated film has a thickness of about fifteen-hundredths (0.15) inch prior to the time when the aggregates are deposited onto the tacky heated film.
3. The process, as described in paragraph 1, wherein step (d) is performed immediately after step (c) so that the tacky heated film does not have an opportunity to cool appreciably prior to contact with the aggregates.
4. The process, as described in paragraph 1, wherein step (b) is carried out so that the flowable mixture has a temperature of approximately two hundred twenty (220) to two hundred fifty (250) degrees Fahrenheit.
5. The process, as described in paragraph 1, wherein the synthetic rubber latex is a copolymer of styrene and butadiene.
6. The process, as described in paragraph 5, wherein the synthetic rubber latex is in the form of finely divided particles; and step (a) comprising the tub-step of uniformly distributing the rubber latex particles throughout the flowable mixture.
7. The process, as described in paragraph 5, wherein said anti-stripping agent serves as a bonding agent between the aggregates, asphalt, and the rubber latex particles.
8. The process, as described in paragraph 5, wherein step (a) is carried out so that the concentration of the rubber latex in the flowable mixture is about one half (1/2) to one and one-half (11/2) percent.
9. The process, as described in paragraph 1, wherein the aggregates comprise crushed rock having a particle size no greater than one (1) inch.
10. The process, as described in paragraph 1, wherein the aggregates comprise sand.
11. The process, as described in paragraph 1, wherein the waste oil is selected so that when a sample of the flowable mixture is subjected to a distillation test at a temperature of five hundred (500) degrees Fahrenheit, less than five (5) percent of the waste oil in the sample will be vaporized.
12. The process, as described in paragraph 1, wherein the waste oil in the flowable mixture has a flash point measuring at least one hundred seventy-five (175) degrees Fahrenheit.
13. The process, as described in paragraph 1, wherein step (c) is carried out so that the tacky heated film has a coverage rate of about two-tenths (0.2) to three-tenths (0.3) gallon per square yard of road surface.
14. A process for resurfacing roads comprising:
(a) mixing from about sixty (60) to about ninety-five (95) parts asphalt from about forty (40) to about five (5) parts waste oil, from about one-half (1/2) to one and one-half (11/2) parts rubber latex, and about one-half (1/2) part anti-stripping agent, to form a flowable mixture;
(b) heating said flowable mixture to a temperature between from about two hundred twenty (220) degrees Fahrenheit to about two hundred fifty (250) degrees Fahrenheit;
(c) spraying said heated flowable mixture onto a road surface to form a tacky heated film on the road surface;
(d) depositing a layer of aggregates onto said tacky heated film; and
(e) pressing the aggregates into said tacky heated film to form a new road surface.
15. The process, as described in paragraph 14, and further comprising the step of shredding the rubber latex into latex particles prior to step (a), whereby the latex is in particulate form in the flowable mixture.
16. The process, as described in paragraph 15, wherein the rubber latex is a copolymer of styrene and butadiene in finely divided form.
17. The process, as described in paragraph 14, wherein the waste oil has a flash point measuring at least one hundred seventy-five (175) degrees Fahrenheit.